1995 Honda Del Sol Si, D16Z6, Automatic. I've attached a couple of audio clips below. Please give them a listen. At a cold startup, first there is a loud whining noise that goes away fairly quick but then a random spitting or hissing sound comes in. After the engine warms up to normal operating temp all the noises seem to go away and the engine runs fine. I'm in hopes that someone can recognize the noises and point me in a direction. I've went over everything I can think of. This all started after replacing a bad head gasket. The noises didn't exist prior to replacing head and intake manifold gaskets. I cleaned spark plugs, replaced distributor, removed and cleaned fitv and iacv, checked valve lash, retorqued intake manifold nuts, replaced fuel pulsation damper, cleaned fuel injectors and replaced seals. I'm at a loss. The occasional heavy thumping noise is me tapping on different things to see it there would be any change. I hope someone can help. It would be much appreciated. I had created a previous thread on this subject but couldn't figure out how to edit or delete it, hence the new thread.

 

Update: I did some more investigating last night and I now believe the swooshing sound is not coming from the intake manifold but rather from the oil pump area. The squealing sound at cold startup is definitely coming from oil pump area. I removed all the belts to isolate it. Once the oil pump stops squealing after a few seconds, I can faintly hear the random swooshing sound from under the oil pan at the oil pump side. It resonates up to around the intake manifold making it sound like it is coming from intake. Going to drop the oil pan next and see what's going on in there.

 

Update: Dropped the oil pan and fortunately found nothing remarkable in the oil or oil pan. Inspected rod and camshaft bearings. No slack in anything at all and no shiny spots like anything was spun, scraped, etc... I'm actually impressed how tight the bottom end is at 277K miles. At this point, I'm expecting all the trouble to be limited to the oil pump which I have not yet removed but that is the next step. I'll post update asap.

 

Resolution : The culprit was the oil pump. After removing, I looked inside the pump and there is definitely scrape marks inside. Replaced oil pump and all is good. No more weird noises at startup and engine runs great. Maybe someone will benefit from this post if they start having any very odd noises from a cold startup that go away as the engine warms up.

 

This a good find and definitely would be helpful information for someone.

 

Good catch. These oil pumps last virtually forever in most cases but it's super good that you caught it before it became catastrophic.